Thesis
Spread of Colletotrichum coccodes from infected potato seed tubers and effect of fungicides on stem infection
Washington State University
Master of Science (MS), Washington State University
2008
Handle:
https://hdl.handle.net/2376/102273
Abstract
Colletotrichum coccodes, the cause of potato black dot is one of several seedborne pathogens. The quality of seed-tubers would likely improve if the interactions between seedborne inoculum and the crop were better understood. The rate of spread of C. coccodes from the seed-tuber was quantified on roots and stolons of 'Russet Burbank' plants grown in the greenhouse. The effect of seedborne inoculum of C. coccodes on final disease severity and potato yields was assessed in the field, and specific fungicides were evaluated for disease management. Expansion of C. coccodes foci along roots in two trials resulted in a linear growth model of 1 mm/day (P < 0.01, R2 = 0.83). Colonization always radiated from the seed-tuber to form compact foci of infected tissue. In the field, severity of host plant colonization in belowground stems was related to percentage of infected tubers in seed lots in two of four fields (P < 0.05). Yields were not related to percentage of seed-tubers infected with C. coccodes (P > 0.1). Black dot was not a yield limiting factor under the conditions of this study, but differences in yield among seed lots (P < 0.05) from other factors illustrated the importance of selecting the highest quality seed available to maximize yields. A live plant stem assay was used to evaluate the effect of fungicide application timing and active ingredient on C. coccodes. Fungicide application by center pivot irrigation (chemigation) in commercial potato fields was evaluated as a potential black dot management strategy. Fungicide application post-inoculation did not significantly reduce infection. Several fungicides were successful in preventing infection by C. coccodes when applied prior to inoculation (P < 0.05). Belowground stems were sampled from the areas where azoxystrobin was chemigated onto the crop at 50- and 67-days after planting (DAP). Less stem surface area was covered with microsclerotia in treated areas at 79 DAP in both years (P < 0.04), but consistent differences between treated and non-treated areas were not detected at 102- and 140-DAP.
Metrics
7 File views/ downloads
26 Record Views
Details
- Title
- Spread of Colletotrichum coccodes from infected potato seed tubers and effect of fungicides on stem infection
- Creators
- Jason Timothy Ingram
- Contributors
- Dennis A. Johnson (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Plant Pathology, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525155101842
- Language
- English
- Resource Type
- Thesis